1. Field of the Invention
The present invention relates to a slider with locking mechanism for use in ordinary slide fasteners, and more particularly to a slider for slide fastener with locking mechanism whose pawl body having locking pawl is actuated to operate the locking mechanism when a pull tab is raised or hung by using a repellent force of the fastener element, without use of any spring.
2. Description of the Related Art
A conventional example for a slider for slide fastener with locking mechanism of this kind is disclosed in Japanese Utility Model Publication No. 45-2165, as shown in FIG. 15. A cut-out is provided by cutting out the center of the surface of an upper wing plate 005 of a slider body 001 in a curved shape, and a pawl hole 013 is provided at a deviated position of the bottom portion of this cut-out. A leaf spring is disposed in the cut-out such that it moves freely and has a U-shaped protruding portion provided in the center thereof, which is capable of entering or escaping from the pawl hole 013 freely. An end of the leaf spring is fixed in a concave portion 011 provided at an end portion of the cut-out. Then, a cam 030 provided on a top portion of a pull tab 003 journalized by a post provided in the upper wing plate 005 is brought into contact from above. By raising or hanging the pull tab 003, the U-shaped protruding portion of the leaf spring is made to protrude in between fastener elements on one side so as to lock the slider.
According to Japanese Patent Application Laid-Open No. 10-127312, a slider for slide fastener having locking mechanism as shown in FIG. 16 has been disclosed. The slider comprises a slider body 101, swing plate, cover 104 and pull tab 103. A recess 111 is provided in a top surface of the upper wing plate 105, a pawl hole 113 is formed on one side in the rear side of the recess 111 and a hook-shaped cover mounting post 118 is provided on front and back, a bearing projecting portion 114 is provided on both sides, the swing plate is formed of a sheet body curved in a gentle V shape, a step is provided for preventing a contact of the cam 130 on the rear surface thereof, and a circular head portion facing downward is provided on one end and a lock projecting portion 124 deviated to one side is provided on the other end. A cam 130 is provided integrally in the center of a pintle on one end of the pull tab 103 and an end of the cam 130 is deviated toward a front end with respect to the axis of the pintle of the pull tab 103. Then, the swing plate is disposed within the recess 111. The pintle of the pull tab 103 is placed on the bearing projecting portion 114 from above, so that the cam 130 is brought into contact with the rear surface of the swing plate and then, the cover 104 is mounted on the mounting posts 118. A projecting piece provided on the cover 104 is brought into contact with the circular head portion of the swing plate. As a result, the swing plate is prevented from floating up freely to lose the locking function when the pull tab 103 is hung.
In the slider for slide fastener with locking mechanism shown in FIG. 15 described above, when considering a contact point between the cam 011 of the pull tab 003 and leaf spring, there may be a problem that when the locking function is actuated by hanging the pull tab 003, the pull tab 003 may jump up due to a force which pushes up the U-shaped protruding portion by engaging elements and a restoration force of the leaf spring i.e. a sliding backward thereof, which makes the locking function unstable. Further, because the protruding portion of the leaf spring is only curved in a U shape, it is easily deformed so that a secure locking function cannot be expected.
In the slider for slide fastener with locking mechanism shown in FIG. 16, when the swing plate is pressed by the cam 130 so that a lock projecting portion 124 formed on the swing plate is pressed into coil-shaped fastener elements, there is a large gap between the lock projecting portion 124 for receiving a repellent force from the fastener element and a contact portion between the cam 130 and swing plate. Therefore, the swing plate is twisted around the contact portion with the cam 130 by a repellent force of the fastener elements, so that it is deformed, thus the lock projecting portion 124 is unable to carry out a sufficient locking action for the fastener elements. Further, the lock projecting portion 124 of the swing plate is deviated to one side, so that the locking function is actuated by only the fastener elements on one side. As a result, the locking function cannot be exerted uniformly to the right and left sides.